Pollution-free coal-preheating with waste heat from dry coke-quenching

ABSTRACT

In order to provide a source of dry preheated coal to be supplied to a coke oven, an inert completely dry gas is directed through a body of hot coke which has just been discharged from a coke oven in order to cool the hot coke, which is thus dryquenched, while the inert gas becomes heated. The hot inert gas is then placed directly in contact with the wet coal so that the wet coal is in this way dried and preheated with heat extracted from the coke by the inert gas. After the coal is thus dried and preheated, the inert gas is cleaned, dried and then returned to flow again through a body of hot coke, so that in this way the inert gas is continuously circulated along a closed path extracting heat from hot coke and delivering the heat to wet coal.

United States Patent Kemmetmueller POLLUTION-FREE COAL-PIIZHEATING WITH WASTE HEAT FROM DRY 1 June 10, 1975 3,843.458 10/1974 Kemmetmueller 202/228 Primary ExaminerNorman Yudkoif COKE-QUENCHING E s d Assistant xaminer-D. an ers [75] Inventor. Ilfgland kemmetmudler, Pittsburgh, Attorney Agent or Firm steinberg & Blake [73] Assignee: American Waagner-Bird Company [57] ABSTRACT Inn, Plttsburgh. Pa. In order to provide a source of dry preheated coal to [22] Flledl 1974 be supplied to a coke oven, an inert completely dry [2]] Appl 435,749 gas is directed through a body of hot coke which has just been discharged from a coke oven in order to cool the hot coke, which is thus dry-quenched, while the [52] US. Cl. 201/39; 201/43; 202/150; inert gas becomes heated. The hot inert gas is the 202/228 laced directly in contact with the wet coal so that the P l] ll'lt. Cl C!) 39/ 2 wet Coal is in this way dried and preheated with hem [58] meld Search 202/227 150i 2Ol/39' extracted from the coke by the inert gas. After the 201/43 44 coal is thus dried and preheated, the inert gas is cleaned. dried and then returned to flow again [56] References through a body of hot coke, so that in this way the UNITED STATES PATENTS inert gas is continuously circulated along a closed path 354 4u7 4 1932 janewa 202 223 extracting heat from hot coke and delivering the heat l.8S4 407 4/1932 Janeway 202/228 to wet C03]. 2.289917 7/1942 Lambiotte 202/228 3.728.230 4/1973 Kemmetmucller 202/228 21 Chums, 2 Drawing Figures ll 21 $7465 cuss/r157 i crew/v55 66 l 14 IS; 57466 i 5 i clan/v55 l. 7

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L44)?! C4? u 1 g 94 SCFUBB Y r Pry/[arm ma VENI' I came 0147/5 //4 I)? l e SCRUBBEE l MD calvos/vsze roa /06 f0? 1 POLLUTION-FREE COAL-PREHEATING WITI-I WASTE HEAT FROM DRY COKE-QUENCHING BACKGROUND OF THE INVENTION The present invention relates to coke plants as well as to methods of operating coke plants.

As is already well known, it is highly desirable to make use of heat in coke discharged from a coke oven, so that the energy of this heat which otherwise is wasted can be used to advantage. For this purpose the coke which is discharged from the coke oven is placed in contact with a gas so as to carry out dry-quenching of the coke, and the gas which extracts heat from the coke in this way is then directed through a heat exchanger so that in the heat exchanger heat is taken from the dry-quenching gas which may then be returned to the coke from the coke oven in order to further dry quench coke and extract additional heat therefrom. A second gas which is heated by the heat exchanger may be used for purposes such as drying and preheating coal.

However, arrangements of this type are extremely expensive in that the heat exchanger used to take heat from the dry-quenching gas and deliver the heat to the coal-drying and preheating gas is an extremely expensive unit. In addition such a heat exchanger is complex in its construction, requires a relatively large amount of space, and creates problems with respect to installation and maintenance.

Proposals have already been made for preheating coal, prior to delivery thereof to a coke oven, by placing the coal directly in contact with a dry-quenching gas, but up to the present time the gas as it issues from a dry-quenching bunker has never been used both for drying wet coal and for preheating the coal. In known installations where preheating of coal takes place by directing a dry-quenching gas through a body of coal, there is an unavoidable generation of undesirable water gas. The gas after preheating the coal is circulated back to the coke to carry out dry-quenching, but the gas is not in a dry condition so that considerable disadvantages result from placing such a moisture-laden gas in contact with the hot coke.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a coke plant and coke plant operating method according to which heat exchangers of the above type are not required.

Thus, it is an object of the present invention to provide a coke plant and coke plant operating method according to which an inert gas used for dry-quenching is also used directly for drying and preheating coal prior to delivery of the coal in the dry preheated condition to a coke oven.

Furthermore, it is an object of the present invention to provide a method and apparatus of the above type according to which the gas is returned after drying and preheating the coal to a dry-quenching bunker with the gas being in a perfectly dry as well as clean condition before being returned to the coke.

In addition it is an object of the present invention to carry out the above operations with an inert gas which will maintain the coal out of contact with oxygen during the drying and preheating of the coal.

Furthermore it is an object of the present invention to provide a method and apparatus of the above type according to which the coal is necessarily maintained below a given size prior to delivery to the coke oven.

In addition it is an object of the above invention to provide a method and apparatus of the above type according to which the gas is returned to the dryquenching bunker in a cool condition, with cooling of the gas being brought about also by way of energy derived from the heat extracted from the hot coke.

In addition it is an object of the present invention to provide a method and apparatus according to which the dry and preheated coal may be reliably stored with complete safety in bins prior to delivery to a coke oven in such a way that an inert gas which forms a cushion over dry and preheated coal in bins is also used to make up any losses in the inert gas which circulates along a closed path during the dry-quenching and coal drying and preheating operations.

According to the method of the invention an inert gas is circulated along a closed path while being directed in a perfectly dry state through a body of hot coke shortly after discharge of the latter from a coke oven so that the inert gas will cool the hot coke while extracting heat therefrom, thus raising the temperature of the inert gas. Wet coal is fed to a part of the path to which the thus-heated inert gas travels after passing through the body of hot coke so that the wet coal is dried by direct contact with the heated inert gas. In this way the inert gas is cooled while drying the coal with the heat extracted from the hot coke as a result of the direct contact between the wet coal and the heated inert gas. The coal which is dried in this way is delivered to a coke oven while the inert gas is cleaned, dried, and then returned along the closed path of flow thereof to a body of hot coke to again be heated by the latter before again returning to the location where the wet coal is situated in order to be dried by the heated inert gas. Preferably the temperature of the inert gas which contacts the wet coal is sufficiently high to bring about not only drying of the coal but also preheating thereof, so that in this way a dry preheated coal is available for supply to the coke oven.

With the apparatus of the invention a dry-quenching bunker means is provided to contain a body of hot coke received from a coke oven, and a coal-drying means is provided for drying coal prior to delivery of the coal to a coke oven. A conduit means has one portion extending from the bunker means to the coal drying means and another portion extending from the coal-drying means to the bunker means, so that the conduit means defines with the bunker means and the coal-drying means a closed path along which an inert gas may be circulated for extracting heat from the hot coke in the bunker means during dry quenching of the hot coke and for then drying the coal with heat extracted from the hot coke during direct contact between the coal and the inert gas prior to return of the inert gas to the bunker means. A means is provided at the portion of the conduit means carrying gas from the coal-drying means to the bunker means for cleaning and drying the gas, so that the inert gas is completely free of moisture when reaching the hot coke.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of the application and in which FIGS. IA and 1B, which are a continuation of each other, illustrate schematically one possible method and apparatus according to the present invention,

DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 13. there is schematically illustratcd at the right thereof it dryouenching bunker which is charged with hot coke pushed out of a col-re oven. For this purpose the hot coke is charged into the bunker it) through the top end thereof which in a known v ry is provided with n closure assembly 1.2. Thus. this assembly 12 closes off the interior of the bunker it; from the outer atmosphere. and the closure assembly 3 is cupublc of being opened in a known way to receive a charge of hot coke directly from a coke oven. these operations prclerubly being carried out in such :1 way that there is no escape of pollutants to the oute atmosphere. After the Ct lLL' is cooled in the dryt'lurnching bunker it) it is discharged out oi the lower dis hurgc end 11 thereof also in a known way. At the lower end l-i the bunker H) is provided with suitable gates which are known and which control the discharge of the cooled coke from the coke oven. this tokc being screened und delivered to suitable bins where it is available for use in blast furnaces, for example. When the coke is discharged f om the dry-quenching bunker lfi it has a temperature on the order of fifl -itl F, since at this temperature the coke has been cooled sulficientiy so that will not burn belt conveyers.

l he interior of the dry-quenching bunker l0 communicates with a pressure release valve it: for safety purposes.

According to a par icular feature of the invention it will be apparent from the description which follows tinit during the dry-quenching thcrr is no generation of Wtilc'l' 1n the dryutlenclling bunker. This is one of thc important advantages achieved with the method and :ipparutus of the invention.

The inert gas which flows upuuirdly through the hot col-re in older to cool that latter while extracting heat therefrom is preferably nitrogen or Lt mixture of nitrogen and carbon dioxide. This inert gas fed in a pen lectly dry condition to the lower end region ol the bunker lit by may of u recirculating fun 18 which drives the 1 ii conduit 20 into the interior of the limiter i r. As is well known at the interior of the bunlt'tr iii the hitter carries a ditching; head 22 in the form ct i: holiow i orrir-oncnt oi"snbstuntiuiiy cii niczrl coniigw rio the interior ol which the inert gals is delivi t d with opcn t in; to litW f, the body oi hot raise in buniicr i ga r 1 us out o 'the lui i cr lit at ti tempera or" tit l -hi b' if and iziirriedi; .ly gion oi" the bur :er thicott'w tiir lgli tlz: ninlticyclrtne is removed l'toni the inert gas, This t is r .lll gil lt o unbustinlc product and ltltl he used t up; do r The l cit glib ch is in this way cleaned by the muliicveltnic unit 24 rind which has the above tcrpperuture on t n; order of titltl R50 f? then is eceived by u site-urn t i |1ie'.'ir.-- it! in tire lorm c 11 while heal boiler oils Pili ll Illu trated.

timing ripper coils llilfl hm n dr mr from which the steam is delivered through suitable stcam'main 34 to any desired location where use will be made of the steam which is generated in this way.

Part of the inert gas, which is still in a perfectly dry condition. is returned from the steam generating means 26 to a conduit 36 which communiates with the suction end of the recirculating fan 18, and through the conduit 36 the perfectly dry inert gas is returned to the fan 18 to be delivered thereby to the bunker 10 as described above The proportion of inert gas from the steam generating means 26 which is mixed with the inert gas flowing along the conduit 36 can be controlled by a valve 38 in the conduit 40 which communicates with the conduit 36 and with the lower end region of the steam generator 26. It will be noted that additional dust is delivered out of the steam generator 26. This dust also is combustible and forms a valuable product. Gen- 7 r the inert gas flowing along the conduit 40 to the conduit .36 will have a temperature on the order of flOtl lftl C and approximately 30 percent of the gas delivered by the fan 18 to the bunker 10 will be derived from the conduit 40 the remaining 70 percent being derived through the conduit 36 which in a manner described below delivers a cool dry inert gas to the fan 18, this latter gas which flows along the conduit 36 to join with the gas from the conduit 40 having a temperature on the order of 0l0" C in this way the temperature or the gas flowing into the bunker 10 can be controlled. in other words by operating the damper or valve 38 it is possible to control the proportions of the inert gas derived from the conduits 36 and 40 so as to regulate the temperature of the inert gas which is delivered to the bunker It). At the same time it is possible to control the temperature of the inert gas discharging out of the steam generator means 26 through the conduit 42 by controlling the flow of cool boiler feed water into the steam generator 26 through the supply conduit 44. in this way it is possible to maintain a relatively constant predetermined temperature for the dry inert gas which is used for drying and preheating coal as described be low. The flow of the inert gas from the the steam gener utor means 26 along the conduit 42 is controlled by a valve or damper 46, and the arrangement is such that a completely dry gas having a temperature on the order of nutr ent C flows out of the steam generator means 2s along the conduit 42. Of the inert gas which flows to the waste-bent boiler 26 from the bunker l0, approxhnntely two thirds of the will flow out of the boiler is along the conduit 42 while the remaining inert gas "will llo-w along the conduit 40 to be recirculated back :11 the bunker by way ofthe fan 18 together with the re muining cool inert gas derived from the conduit 36 uperun of its connection with the conduit 40.

The conduit 42 may he provided with an auxiliary gas burner 18 for starting purposes, this unit being used oniy at the beginning ofau operating cycle, and the initinl heating provided by way of the unit 48 will serve to pct! :ratc is certain amount of inert gas. Part of the dust tlisclmrgotl out of the units 24 and 26 may be used in the nuxi iary gus burner 48a itcl'trring now to FIG. 1A, it will be seen that the perf ctly dry inert gas which in the above example is at a rw-riipcrnture on the order of 600-o50 C reaches a trmlvlrying means St). in the illustrated example the L-"::l-t|? r ng on runs 50 is at twostagc dryer, and the hot. flows through the second stage 52 of Wilt) 5t] before reaching the first stage 54 thereof. With the illustrated coal-drying means 50, the coal is dried in a countercurrent manner with respect to the flow of inert gas in the sense that the second stage 52 is situated upstream of first stage, but in each stage the coal flows concurrently with the gas so that concurrent drying takes place in each stage of the coal-drying means while the stages thereof are arranged in a countercurrent manner with respect to the flow of inert gas.

It is to be understood that although a two-stage dryer is illustrated in FIG. IA and described in detail below, the invention can equally well be used with a single stage dryer or with a fluidized bed type of coal dryer installation.

The first stage dryer unit 54 is in the form of an elongated tubular structure which has an upstream end region 56 communicating with a conduit 58 through which the heated inert gas flows into the tubular structure of the first stage unit 54 in order to dry coal therein. The wet coal is fed in a crushed particulate form, after passing through suitable crushing mills as is well known, into the tubular structure of the dryer unit 54 at the region of the upstream end 56 thereof. Thus FIG. 1A shows schematically a wet coal feed means 60 which serves to feed the wet coal in particulate form into the tubular structure of the first stage unit 54. The particles of wet coal become suspended in the flowing stream of inert gas to be be carried along with the gas, while being dried thereby, toward the downstream end region 62 of the unit 54. This end region 62 is provided with a pair of classifier units 64 and 66. Thus. as the particles of coal suspended in the inert gas flow with the latter toward and through the curved end region 62 of the unit 54, the larger and therefore heavier coal particles will discharge out of the classifier outlet 64 while the smaller and lighter coal particles will discharge out of the subsequent classifier outlet 66. In this way a classification is carried out to separate particles which are larger than a given size from coal particles which are smaller than a given size.

In accordance with one of the features of the invention the particles larger than a given size which discharge out of the classifier outlet 64 are carried along with part of the inert gas through a conduit 68 to a hammer mill 70 which is situated outside the path of flow of the inert gas and the coal suspended therein, and in the hammer mill the size of the particles is further reduced after which the particles of reduced size are returned to the tubular structure of the first stage dryer unit 54 through a conduit 72, as schematically represented in FIG. 1A. Thus the invention provides outside of the path of flow of the inert gas and the coal suspended therein a means for reducing the size of coal particles which are greater than a given size. with the particles which have their size thus reduced being returned to the tubular structure of the coal dryer to again flow along with the inert gas toward the downstream end region 62 where the classifier means 64, 66 is situated. In this way the particles of coal which flow with the inert gas beyond the first stage of the dryer means 50 along the conduit 74 will necessarily be no larger than a given grain size. The inert gas with the coal particles suspended therein is received by a first stage cyclone means 76 wichh includes a number of cyclones in which the particles of coal dried at the first stage 54 are separated from the inert gas. The inert gas continues to flow beyond the cyclone separator means 76 along a conduit 78 where the inert gas has a temperature on the order of 1 10 C.

The particles of coal which are discharged from the cyclone means 76 are received by a conveyer means 80 such as a suitable screw conveyer, as schematically illustrated, and these particles of coal which are dried in the first stage unit 54 are delivered by the conveyer 80 through a conduit 82 into an upstream end region 84 of the tubular structure 86 which forms the second stage unit 52 of the coal-drying means 50. Of course in this second stage unit 52 the temperature of the inert gas is higher than in the first stage unit 54, the temperature of the gas at the second stage being on the order of 600 C, as pointed out above. In the second stage unit 52 the coal particles flow together with the inert gas toward the upstream end of the conduit 58 which interconnects the first and second stages, and in this second stage unit 52 the coal not only has been completely dried but is preheated to a temperature well above the ambient temperature so that coal in completely dry and preheated condition is discharged out of the second stage 52 of the coal-drying means 50. The downstream end of the second stage unit 52 communicates also with a cyclone means 88 which include a plurality of second stage cyclones in which the inert gas is separated from the dry and preheated coal. This inert gas which is thus separated from the particles of coal at the second stage then flows through the conduit 58 to the first stage.

The dry and preheated coal is received from the sec 0nd stage cyclone means 88 by a conveyer means 90 which may also take the form of a suitable screw conveyer. It is to be noted that during drying and preheating the coal has been maintained entirely out of contact with oxygen.

The conveyer means 90 delivers the dry preheated coal to a plurality of hot coal bins 92 which form a bin means in which the dry, preheated coal is temporarily stored prior to delivery to a larry car installation 94 which serves in a known way to deliver the dry, preheated coal to the coke ovens as schematically illustrated in FIG. 1A. The gas which discharges from the larry car unit 94 is delivered to a scrubber means 96 where the gas is cleaned before being discharged to the outer atmosphere so that pollution is in this way avoided, a suitable blower 98, or the like, being provided to draw the gases out of the larry car unit 94 and through the scrubber means 96 before discharging the clean gas to the outer atmosphere.

In the event that the system used for transfer of the hot coal from bin means 92 to the coke ovens is relatively tight with respect to the outer atmosphere, the gas discharged after the scrubber 96 by the fan 98 will still for the most part be in the form of an inert gas, and in this case the inert gas can be returned to any desired part of the closed path of flow along which the inert gas circulates in accordance with the invention. as will be apparent from the further description below.

In accordance with one of the futher features of the present invention, for safety purposes an inert gas derived from any suitable source such as a nitrogen tank or the like is delivered to the interior of the bins 92 into upper regions thereof to form an inert gas cushion over the dry preheated coal which is temporarily stored in these bins. In this way an extremely safe installation is provided free of any possibility of undesirable explosions. The inert gas which thus forms the gas cushions over the dry. preheated coal in the bins 92 is capable of escaping through the conveyer means 90 into the second stage cyclone means 88 to be combined with inert gas flowing through the second stage dryer unit. so that in this way the inert gas which forms the gas cushions above the preheated coal in the coal bins also serves to make up any losses in the continuously circulating inert gas which flows first through the bunker l and then through the coal-drying means 50.

The inert gas which flows along the conduit 78 from the first stage cyclones 76 is delivered to a scrubber and condenser means 100. The scrubber means 100 thus receives the cooled inert gas which has a temperature on the order of 100 C together with water vapor which has been removed from the coal during the drying thereof. in the scrubber and condenser means 100 the water is quenched out of the gas. The scrubber means 100 may be a single or two-stage scrubber and spray water is pumped into the scrubber means 100 by way of a suitable pump 102. After traveling through the scrubber the gas flows through a demister unit 104 which serves further to remove any moisture from the gas. with the liquid which is removed being delivered to a clarifier means 106 which discharges the condensate and slurry. Make-up water if required is delivered to the clarifier 106 with this water being delivered to the spray water pump I02. At the same time the gas which has been dried flows from the demister unit 104 along a conduit 108 to the inlet of the system fan 110 with part of the gas being discharged to the outer atmosphere through a suitable vent unit 112 controlled by a valve or damper 114, so that in this way balanced operating conditions are maintained.

The gas in conduit 108 is a saturated gas at the dew point temperature of 30-40 C. This gas has on the order of 0.02 grams of water in each cubic meter of gas.

The system fan 110 delivers the inert gas to a conduit 116 which serves to deliver the inert gas to a cooling means 118. A conduit 120 may be provided if desired to interconnect the conduits 116 and 42. This conduit 120 is optional. it may be used to deliver part of the inert gas directly from fan 110 to the conduit 42 in order to be combined with the hot inert gas from the steam generating means 26 before reaching the second stage dryer unit 52. If the connecting conduit 120 is provided, it will be equipped with a valve or damper 122 enabling the proportion of gas which flows from the conduit 116 to the conduit 42 to be regulated.

As has been indicated above the inert gas may be a mixture of nitrogen and carbon dioxide and this inert gas flows from the demister unit 104 to the system fan 110 at a temperature on the order of 30-40 C. In addition desulfurization, if necessary, is carried out at the demister unit 104. In this way a relatively cool. relatively dry, clean gas is delivered to the recirculating gas cooler means 118.

This cooling means 118 forms part of a refrigerating unit in which through suitable coils a refrigerant is circulated as by a compressor means 124, suitable cooling water being directed through a section 126 of the cooling means as illustrated in FIG. 1B. The cooling installation 118 will include suitable compressors 124 which must be driven. and for this purpose in accordance with a further feature of the invention steam is tapped from the main 34 and delivered by way of a conduit 128 to the steam turbine unit 130 of the cooling means 118 so as to drive the compressors 124 thereof. Condensate from turbine 130 is delivered by conduit 131 to unit 126 together with the cooling water and is then fed by a pump and conduit to feedwater supply 44.

As a result of the cooling action taking place at the cooling means H8, the temperature of the gas is lowered to the order of 05 C. and all moisture in the gas is condensed out of the gas at the cooling means H8, with the condensate being received by the conduit 132 which serves to deliver the condensate to the condensate treating unit 134 from which gas is discharged by the conduit 136 while the condensate is discharged by the outlet 138.

In this way a perfectly dry, chilled inert gas is delivcred along the conduit 36 to be combined with part of the gas flowing along the conduit 40 from the steam generating means 26, as described above, enabling in this way the temperature of the dry inert gas which is delivered to the bunker 10 to be precisely regulated.

It is apparent, therefore, that with the method and apparatus of the invention a closed path of flow is provided for the inert gas, this closed path of flow having the body of hot coke through which the inert gas flows, at one part of the closed path. and a coal-drying means 50. to which the wet coal is delivered, at another part of the closed path. It will be noted that an extremely efficient operation is achieved. making full use of the waste heat from the dry coke-quenching. Furthermore it will be noted that there is no generation of water gas as a result of the flow of the inert gas through the hot coke in the bin 10. Full use is made of the energy of the waste heat from the dry coke-quenching by utilizing this heat not only for drying the wet coal initially but also for preheating the coal so that the coal is in a preheated as well as dry condition when delivered to the coke ovens. The situation of the hammer mill at the exterior is also of advantage since in this way the hammer mill is not influenced by the heat and vapors in the dryer itself. Moreover it will be seen that throughout the entire system of the invention there is never a location where any gas with pollutants therein can escape to the outer atmosphere so that with the system of the invention there is no problem in connection with pollu tion of the atmosphere. Furthermore, the installation does not include any expensive heat exchanging units and is for the most part relatively inexpensive as well as highly efficient in its operation.

What is claimed is:

1. In a method for operating a coke plant. the steps of circulating an inert gas along a closed path, directing the inert gas as it circulates along said closed path through a body of hot coke shortly after discharge of the body of hot coke from a coke oven so that the inert gas cools the hot coke while extracting heat therefrom to raise the temperature of the inert gas. feeding wet coal to a part of the path to which the thus-heated inert gas travels after passing through the body of hot coke so that the wet coal is dried by direct contact with the heated inert gas, thus cooling the inert gas while drying the coal with heat extracted from the hot coke during direct contact between the wet coal and the heated inert gas, delivering the thus-dried coal to a coke oven, returning the inert gas along a return part of said closed path from the location where coal drying takes place back to a body of hot coke to again be heated by the latter before again returning to the location where the wet coal is situated to be dried by the heated inert gas. and completely drying the inert gas as it travels along the return part of the closed path to a body of hot coke so that the inert gas is in a moisture-free condition when reaching the body of hot coke.

2. In a method as recited in claim 1 and including the step of cleaning the gas before it returns to the hot coke.

3. In a method as recited in claim 1 and wherein the temperature of the inert gas when it contacts the wet coal is sufficiently high not only to dry the coal but also to elevate the temperature thereof to a temperture substantially above the ambient temperature, for preheating the coal, and delivering the coal in a dry preheated condition to the coke oven.

4. In a method as recited in claim 1 and wherein the dry coal is delivered to a bin before being delivered to the coke oven, and including the step of maintaining a cushion of the inert gas over the dry coal in said bin.

5. In a method as recited in claim 4 and wherein the inert gas cushion in said bin communicates with said closed path for making up any losses of inert gas from said closed path.

6. In a method as recited in claim 1 and including the step of partially cooling the inert gas after it flows through the body of hot coke but before it reaches the location to which the wet coal is fed so that the coal is dried with the inert gas at a temperature of the inert gas which is less than the temperature of the inert gas as it leaves the body of hot coke.

7. In a method as recited in claim 6 and wherein steam is generated with heat extracted from the inert gas during the partial cooling thereof.

8. In a method as recited in claim 7 and wherein the gas-drying step includes cooling the inert gas to condense moisture therefrom just before it returns to a body of hot coke, while utilizing at least as part of a source of energy for cooling the inert gas at least some of the steam generated with the inert gas during the partial cooling of the latter.

9. In a method as recited in claim 1 and wherein the gas-drying step includes cooling the inert gas to condense moisture therefrom just before it reaches a body of hot coke for extracting heat therefrom.

10. in a method as recited in claim 1 and including the steps of extracting from the location to which the wet coal is delivered to be dried by contact with the inert gas coal particles greater than a given size, reducing the size of the extracted coal particles at a location situated outside of the closed path and then returning the coal particles which thus have been reduced in size back to said closed path at the location to which the wet coal is delivered, so that the coal which is dried includes only particles which are smaller than a given size.

1]. ln a coke plant, dry-quenching bunker means for containing a body of hot coke received from a coke oven, coal-drying means for drying coal prior to delivery of the coal to a coke oven, conduit means having one portion extending from said bunker means to said coal-drying means and another portion extending from said coal-drying means to said bunker means, so that said conduit means defines with said bunker means and coal-drying means a closed path along which an inert gas may be circulated for extracting heat from hot coke in said bunker means during dry-quenching of the hot coke and for then drying coal with heat extracted from hot coke during direct contact between the coal and the inert gas prior to return of the inert gas to the bunker means, and gas-drying means operatively connected with that portion of the conduit means which delivers the inert gas to said bunker means for extracting all moisture from the inert gas, so that the inert gas is in a completely dry condition when reaching the bunker means.

12. The combination of claim I] and wherein a steam-generating means is operatively connected with that portion of said conduit means which receives the heated inert gas from said bunker means for partially cooling the inert gas, while generating steam therefrom, prior to the drying of coal at said coal-drying means with the inert gas.

13. The combination of claim 11 and wherein a gascleaning means is operatively connected with said conduit means for cleaning the inert gas.

14. The combination of claim 11 and wherein said gas-drying means includes a gas-cooling means operatively connected with that portion of the conduit means which delivers the inert gas to said bunker means for condensing moisture out of the inert gas.

15. The combination of claim 14 and wherein a steam generating means is operatively connected with that portion of the conduit means which delivers the inert gas from the bunker means to the coal-drying means for partially cooling the inert gas while generating steam therefrom prior to drying of the coal with the inert gas, and means for directing part of the generated steam from said steam-generating means to said gascooling means for operating the latter at least partially with steam generated from the inert gas during the partial cooling thereof.

16. The combination of claim 11 and wherein a means is situated outside of said coal-drying means but communicates therewith for receiving particles of coal above a given size from said coal-drying means and for reducing the size of the coal particles before returning the latter to said coal-drying means.

17. The combination of claim 11 and wherein a conveyer means communicates with said coal-drying means for conveying dry coal away from the latter, bin means communicating with said conveyer means for receiving the dry coal therefrom and storing the dry coal prior to delivery thereof to a coke oven, and inert gas supply means communicating with said bin means for maintaining a cushion of inert gas over dry coal stored at said bin means.

18. The combination of claim 17 and wherein said bin means communicates through said conveyer means with said coal-drying means for utilizing part of the inert gas supplied to said bin means to form said cushion to make up losses of inert gas from the closed path of travel of the inert gas.

19. The combination of claim 11 and wherein a larrycar means communicates with said bin means for transferring coal therefrom to a coke oven and gas-cleaning means communicating with said larry-car means for cleaning the gas discharged therefrom.

20. The combination of claim 11 and wherein said coal-drying means includes an elongated tubular structure having an upstream end connected to said one portion of said conduit means which receives the inert gas from said bunker means and a downstream end portion from which the inert gas flows after drying coal in said elongated tubular structure. means for delivering wet coal to the region of the upstream end of said tubular structure, and cyclone means operatively connected structure so that the latter forms a second stage of said coal-drying means, an additional cyclone means being situated between said tubular structures for separating the gas from the coal dried in said second tubular structure. and conveyer means communicating with said additional cyclone means for conveying the dry coal away from the latter.

* =l= i i 

1. IN A METHOD FOR OPERATING A COKE PLANT, THE STEPS OF CIRCULATING AN INERT GAS ALONG A CLOSED PATH, DIRECTING THE INERT GAS AS IT CIRCULATES ALONG SAID CLOSED PATH THROUGH A BODY OF HOT COKE SHORTLY AFTER DISCHARGE OF THE BODY OF HOT COKE FROM A COKE OVEN SO THAT THE INERT GAS COOLS THE HOT COKE WHILE EXTRACTING HEAT THEREFROM TO RAISE THE TEMPERATURE OF THE INERT GAGAS, FEEDING WET COAL TO A PART OF THE PATH TO WHICH THE HUSHEATED INERT GAS TRAVELS AFTER PASSING THROUGH THE BODY OF HOT COKE SO THAT THE WET COAL IS DRIED BY DIRECT CONTACT WITH THE HEATED INERT GAS, THUS COOLING THE INERT GAS WHILE DRYING THE COAL WITH HEAT EXTRACTED FROM THE HOT COKE DURING DIRECT CONTACT BETWEEN THE WET COAL AND THE HEATED INERT GAS, DELIVERING THE THUS-DRIED COAL TO A COKE OVEN, RETURNING THE INERT GAS ALONG A RETURN PART OF SAID CLOSED PATH FROM THE LOCATION WHERE COAL DRYING TAKES PLACE BACK TO A BODY OF HOT COKE TO AGAIN BE HEATED BY THE LATTER BEFORE AGAIN RETURNING TO THE LOCATION WHERE THE WET COAL IS SITUATED TO BE DRIED BY THE HEATED INERT GAS, AND COMPLETELY DRYING THE INERT GAS AS IT TRAVELS ALONG THE RETURN PART OF THE CLOSED PATH TO A BODY OF HOT COKE SO THAT THE INERT GAS IS IN A MOISTURE -FREE CONDITION WHEN REACHING THE BODY OF HOT COKE.
 2. In a method as recited in claim 1 and including the step of cleaning the gas before it returns to the hot coke.
 3. In a method as recited in claim 1 and wherein the temperature of the inert gas when it contacts the wet coal is sufficiently high not only to dry the coal but also to elevate the temperature thereof to a temperture substantially above the ambient temperature, for preheating the coal, and delivering the coal in a dry preheated condition to the coke oven.
 4. In a method as recited in claim 1 and wherein the dry coal is delivered to a bin before being delivered to the coke oven, and including the step of maintaining a cushion of the inert gas over the dry coal in said bin.
 5. In a method as recited in claim 4 and wherein the inert gas cushion in said bin communicates with said closed path for making up any losses of inert gas from said closed path.
 6. In a method as recited in claim 1 and including the step of partially cooling the inert gas after it flows through the body of hot coke but before it reaches the location to which the wet coal is fed so that the coal is dried with the inert gas at a temperature of the inert gas which is less than the temperature of the inert gas as it leaves the body of hot coke.
 7. In a method as recited in claim 6 and wherein steam is generated with heat extracted from the inert gas during the partial cooling thereof.
 8. In a method as recited in claim 7 and wherein the gas-drying step includes cooling the inert gas to condense moisture therefrom just before it returns to a body of hot coke, while utilizing at least as part of a source of energy for cooling the inert gas at least some of the steam generated with the inert gas during the partial cooling of the latter.
 9. In a method as recited in claim 1 and wherein the gas-drying step includes cooling the inert gas to condense moisture therefrom just before it reaches a body of hot coke for extracting heat therefrom.
 10. In a method as recited in claim 1 and including the steps of extracting from the location to which the wet coal is delivered to be dried by contact with the inert gas coal particles greater than a given size, reducing the size of the extracted coal particles at a location situated outside of the closed path and then returning the coal particles which thus have been reduced in size back to said closed path at tHe location to which the wet coal is delivered, so that the coal which is dried includes only particles which are smaller than a given size.
 11. In a coke plant, dry-quenching bunker means for containing a body of hot coke received from a coke oven, coal-drying means for drying coal prior to delivery of the coal to a coke oven, conduit means having one portion extending from said bunker means to said coal-drying means and another portion extending from said coal-drying means to said bunker means, so that said conduit means defines with said bunker means and coal-drying means a closed path along which an inert gas may be circulated for extracting heat from hot coke in said bunker means during dry-quenching of the hot coke and for then drying coal with heat extracted from hot coke during direct contact between the coal and the inert gas prior to return of the inert gas to the bunker means, and gas-drying means operatively connected with that portion of the conduit means which delivers the inert gas to said bunker means for extracting all moisture from the inert gas, so that the inert gas is in a completely dry condition when reaching the bunker means.
 12. The combination of claim 11 and wherein a steam-generating means is operatively connected with that portion of said conduit means which receives the heated inert gas from said bunker means for partially cooling the inert gas, while generating steam therefrom, prior to the drying of coal at said coal-drying means with the inert gas.
 13. The combination of claim 11 and wherein a gas-cleaning means is operatively connected with said conduit means for cleaning the inert gas.
 14. The combination of claim 11 and wherein said gas-drying means includes a gas-cooling means operatively connected with that portion of the conduit means which delivers the inert gas to said bunker means for condensing moisture out of the inert gas.
 15. The combination of claim 14 and wherein a steam generating means is operatively connected with that portion of the conduit means which delivers the inert gas from the bunker means to the coal-drying means for partially cooling the inert gas while generating steam therefrom prior to drying of the coal with the inert gas, and means for directing part of the generated steam from said steam-generating means to said gas-cooling means for operating the latter at least partially with steam generated from the inert gas during the partial cooling thereof.
 16. The combination of claim 11 and wherein a means is situated outside of said coal-drying means but communicates therewith for receiving particles of coal above a given size from said coal-drying means and for reducing the size of the coal particles before returning the latter to said coal-drying means.
 17. The combination of claim 11 and wherein a conveyer means communicates with said coal-drying means for conveying dry coal away from the latter, bin means communicating with said conveyer means for receiving the dry coal therefrom and storing the dry coal prior to delivery thereof to a coke oven, and inert gas supply means communicating with said bin means for maintaining a cushion of inert gas over dry coal stored at said bin means.
 18. The combination of claim 17 and wherein said bin means communicates through said conveyer means with said coal-drying means for utilizing part of the inert gas supplied to said bin means to form said cushion to make up losses of inert gas from the closed path of travel of the inert gas.
 19. The combination of claim 11 and wherein a larry-car means communicates with said bin means for transferring coal therefrom to a coke oven and gas-cleaning means communicating with said larry-car means for cleaning the gas discharged therefrom.
 20. The combination of claim 11 and wherein said coal-drying means includes an elongated tubular structure having an upstream end connected to said one portion of said conduit means which receives the inert gas from said bunker means and a downstream end portion from which tHe inert gas flows after drying coal in said elongated tubular structure, means for delivering wet coal to the region of the upstream end of said tubular structure, and cyclone means operatively connected with said conduit means downstream of the downstream end of said tubular structure for separating the dry coal from the gas prior to return of the latter to said bunker means.
 21. The combination of claim 20 and wherein a second elongated tubular structure is connected with said conduit means upstream of the first-mentioned tubular structure and conveyer means for conveying the dry coal from said cyclone means to said second tubular structure so that the latter forms a second stage of said coal-drying means, an additional cyclone means being situated between said tubular structures for separating the gas from the coal dried in said second tubular structure, and conveyer means communicating with said additional cyclone means for conveying the dry coal away from the latter. 